How to list tables in their dependency order (based on foreign keys)?

I needed to do this myself and was hoping someone had already done it for Postgres, but didn't find anything, so I'll just leave this here:

WITH RECURSIVE t AS (
    SELECT relnamespace as nsp, oid as tbl, null::regclass as source, 1 as level
    FROM pg_class
    WHERE relkind = 'r'
        AND relnamespace not in ('pg_catalog'::regnamespace, 'information_schema'::regnamespace)
UNION ALL
    SELECT c.connamespace as nsp, c.conrelid as tbl, c.confrelid as source, p.level + 1
    FROM pg_constraint c
    INNER JOIN t p ON (c.confrelid = p.tbl AND c.connamespace = p.nsp)
    WHERE c.contype = 'f'
        AND c.connamespace not in ('pg_catalog'::regnamespace, 'information_schema'::regnamespace)
)
SELECT nsp::regnamespace, tbl::regclass
FROM t
GROUP BY nsp, tbl
ORDER BY max(level) DESC;

This is a bit of a hybrid query between two use cases. You may remove the GROUP BY and SELECT source::regclass instead, if you need to see to which table the foreign key refers.

    example:

    create table t1 (i int primary key,j int unique)
    create table t2 (i int primary key references t1 (i));
    create table t3 (i int,j int,primary key (i,j));
    create table t4 (i int,j int,  foreign key (i,j) references t3 (i,j));
    create table t5 (i int references t1 (i),j int,foreign key (i,j) references t3 (i,j));
    create table t6 (i int references t2 (i));

---

with        cte (lvl,object_id,name)
            as 
            (
                select      1
                           ,object_id
                           ,name

                from        sys.tables

                where       type_desc       = 'USER_TABLE'
                        and is_ms_shipped   = 0

                union all

                select      cte.lvl + 1
                           ,t.object_id
                           ,t.name
                from                    cte

                            join        sys.tables  as t

                            on          exists
                                        (
                                            select      null

                                            from        sys.foreign_keys    as fk

                                            where       fk.parent_object_id     = t.object_id 
                                                    and fk.referenced_object_id = cte.object_id
                                        )

                                    and t.object_id <> cte.object_id
                                    and cte.lvl < 30

                where       t.type_desc     = 'USER_TABLE'      
                        and t.is_ms_shipped = 0
            )


select      name
           ,max (lvl)   as dependency_level

from        cte

group by    name

order by    dependency_level
           ,name
;

Thanks for David.

I've just added the schema name to his query if anyone needed

WITH cte (lvl, object_id, name, schema_Name) AS
  (SELECT 1, object_id, sys.tables.name, sys.schemas.name as schema_Name
   FROM sys.tables Inner Join sys.schemas on sys.tables.schema_id = sys.schemas.schema_id
   WHERE type_desc = 'USER_TABLE'
     AND is_ms_shipped = 0
   UNION ALL SELECT cte.lvl + 1, t.object_id, t.name, S.name as schema_Name
   FROM cte
   JOIN sys.tables AS t ON EXISTS
     (SELECT NULL FROM sys.foreign_keys AS fk
      WHERE fk.parent_object_id = t.object_id
        AND fk.referenced_object_id = cte.object_id )
   JOIN sys.schemas as S on t.schema_id = S.schema_id
   AND t.object_id <> cte.object_id
   AND cte.lvl < 30
   WHERE t.type_desc = 'USER_TABLE'
     AND t.is_ms_shipped = 0 )
SELECT schema_Name, name, MAX (lvl) AS dependency_level
FROM cte
GROUP BY schema_Name, name
ORDER BY dependency_level,schema_Name, name;

The above answers won't work with circular references. You can use this stored procedure instead.

EXEC sp_msdependencies @flags = 8

Can see the flag options here

EXEC sp_msdependencies '?'

Unfortunately this is not available on SQL Azure.